44-B1 Isolated transsyndesmotic fibular fracture

The most common injury pattern occurs with axial loading of a maximally supinated (adducted) foot. Subtalar inversion results in external rotation of the talus in the mortise. This causes an oblique fracture of the fibula, starting at the level of the ankle joint and extending proximally from anterior to posterior. This may be a non-displaced crack fracture, if the deforming force ceases at this point. Progressive talar rotation causes posterior displacement of the lateral malleolus, opening the oblique fibular
fracture.

These fractures correspond to the supination-eversion fractures, stages I-II, in the Lauge-Hansen classification.

1. 44-B1.1 Simple

FibulaA simple, oblique fracture occurs at the level of the
syndesmotic ligaments, either minimally displaced or nondisplaced.

Anterior syndesmosisThis is not ruptured.

44-B1.1 AP view

Radiograph taken from Orozco R et al, (1998) Atlas of Internal Fixation. Used with kind permission.

2. 44-B1.2 Simple, with rupture of the anterior syndesmosis

44-B1.2

FibulaA simple, oblique fracture occurs at the level of the syndesmotic ligaments, either displaced or undisplaced.

Anterior syndesmosisThe stress begins at the anterior syndesmotic ligament and results in a ligamentous rupture, or in an avulsion fracture of the anterior syndesmotic ligament's fibular, or tibial, insertion (Lauge-Hansen, SE stage I). Further stress, due to external rotation of the talus, leads to the fibular fracture (Lauge-Hansen, SE stage II). The interosseous ligament is not ruptured.

44-B1.2 AP and lateral view

3. 44-B1.3 Multifragmentary

44-B1.3

Fibula
A multifragmentary fracture occurs at the level of the syndesmotic ligaments.

Anterior syndesmosis
The stress begins at the anterior syndesmotic ligament and results in a ligamentous rupture or in an avulsion fracture of the anterior syndesmotic ligament's fibular or tibial insertion (Lauge-Hansen, SE stage I). Further stress due to continued external rotation of the talus leads to the fibular fracture (Lauge-Hansen, SE stage II).
In the commonest 44 B1.3, a third fragment represents the detachment of the tip of the main proximal fibular fragment. This third fragment usually bears some intact portion of the anterior syndesmotic ligament. It may become entrapped between the main proximal fibular fragment and the lateral malleolar fragment, impeding reduction. The interosseous ligament is not ruptured.

The 44 B1.3 fracture considered here is a truly multifragmentary fracture complex in the trans-syndesmotic zone.

44-B1.3 AP view

Radiograph taken from Orozco R et al, (1998) Atlas of Internal Fixation. Used with
kind permission.